Ignition electrode unit



Filed Oct. 17, 1968 INVENTOR John Hit/W717 BY g 5 ATTORNEY United States Patent 3,505,568 IGNITION ELECTRODE UNIT John H. Flynn, 284 Elk Ave., New Rochelle, N.Y. 10804 Filed Oct. 17, 1968, Ser. No. 768,462 Int. Cl. F2311 3/00; G01v N06 US. Cl. 317-79 10 Claims ABSTRACT OF THE DISCLOSURE Ignition electrode in which the conductor rod, extending through opposite end pieces and a spacer sleeve therebetween, has a shoulder on its electrode carrying end, and a spring between a terminal on the other end of the conductor rod and the nearest end piece thereto urges the conductor rod with its shoulder against the other end piece. Featured is the formation of the conductor rod in two separate rod sections of which adjacent end lengths are threaded for the reception of a coupling by which they are releasably joined within the spacer sleeve, with this coupling being also tightened against the end piece against which the rod shoulder'is spring-urged so that the rod section providing the shoulder is firmly clamped to this end piece.

This invention relates to ignition devices, and more particularly to ignition electrode units, for gas burners.

Igntion electrode units to which the present invention pertains are of the type used especially, though by no means exclusively in bakery ovens and the like, wherefore these units are relatively long to span the heavily insulated and accordingly deep front wall of an oven and afford external terminal connection with wiring as well as provide a sparking electrode in igniting proximity with a gas burner in the interior of the oven. An ignition electrode unit of this type is shown in my prior Patent No. 2,715,200, dated Aug. 9, 1955. However, while this prior unit is generally satisfactory, and is even superior to other prior units by being unaffected by different expansion under heat of different-metal parts thereof, it does have a few drawbacks. Thus, attainment of this superior feature entails rotational play of the electrode-carrying conductor rod in the unit which, while rather slight, is nevertheless objectionable in the important respect to affording the sparking electrode the same play which makes it impossible to lock the same in optimum igniting relation with flame ports of an associated burner. Also, to replace a pitted electrode, it is quicker and less cumbersome to install a new conductor rod with an attached electrode than to try, more or less successfully, to pry the pitted electrode from its conductor rod which is still in perfectly sound condition and, if successful, force into the latter a new electrode which, for its location in proper igniting relation with an associated installed burner, would almost certainly require temporary loosening of the amount of the entire unit for its rotary adjustment for this purpose. Further, while these units may, for different reach of their electrodes in different installations, come in different lengths, this would require either to stock not only different-length spacer sleeves but also differentlength conductor rods, or to resort to equally expensive and additionally time-consuming made-to-order manufacture of these parts.

It is among the objects of the present invention to provide an ignition electrode unit of this type which has none of the aforementioned objectionable aspects of the prior unit and, moreover, has the outstanding feature of the latter unit in being unaffected by different expansion under heat of different-metal parts thereof.

Patented Apr. 7, 1970 It is another object of the present invention to provide an ignition electrode unit of this type in which a preloaded compression spring on the conductor rod is interposed between the end terminal thereon and the nearest end piece on the spacer sleeve in order to urge the conductor rod with a shoulder at its other end against the outer face of the other end piece on this spacer sleeve and thereby hold the unit assembled, as well as to permit mere spring-opposed and, hence, harmless relative longitudinal movement between the different-metal spacer sleeve and conductor rod on their different expansion under heat, the same as in my prior unit, and to further provide for additionally clamping the conductor rod to the one end piece against which the rod shoulder is spring-urged, by tightening a nut on a threaded portion of the rod in the spacer sleeve against the inner face of this one end piece and thereby also drawing the rod shoulder against the outer face thereof with a force which is far greater than that of the spring and fully adequate to lock the rod to this one end piece against relative rotational play between them. In so doing, when the unit is once mounted with its electrode in optimum igniting relation with an associated burner, the electrode will remain locked in this exact relation with the burner.

-It is a further object of the present invention to provide an ignition electrode unit of this type of which the conductor rod is formed in two separate coaxial sections with adjacent threaded ends, of which a main section carries the end terminal and is preferably much longer than the other or secondary section which provides the shoulder and carries the sparking electrode, and the aforementioned clamping nut in the spacer sleeve is a coupling received by the adjacent threaded ends of both rod sections, with this coupling being of conductive metal and serving not only to firmly clamp or lock the secondary rod section to its receiving end piece but also to connect both rod sections. With this arrangement, a pitted electrode may be replaced quickly and at minimum cost by merely disconnecting the rod sections at the coupling and substituting for the short secondary rod section with its pitted electrode an identical new one with an attached new electrode and then reapplying the coupling so that the much longer major rod section will be of continuous use in the unit.

Another object of the present invention is to provide an ignition electrode unit of this type in which the spacer sleeve of heat-resisting steel or the like and the opposite end pieces thereon of usual heat-resisting and electrically insulating ceramic material are preferably kept at usual reasonably small cross-sectional dimensions at which no spark will jump from the conductor rod to the spacer sleeve, but the end piece in which the aforementioned secondary rod section extends is recessed in its inner face to receive in outwardly electrically shielded fashion the coupling between both rod sections and thereby avoid a spark jump gap from this conductive coupling to the nearby surrounding spacer sleeve.

A further object of the present invention is to provide an ignition electrode unit of this type of which the aforementioned conductor rod sections and coupling therefor are arranged for their ready assembly as conductors of considerably varying lengths to adapt the latter to units of different lengths which, except for spacer sleeves of different lengths, require only standard ready-to-use parts for their assembly. This is achieved by making the threaded end of the main rod section particularly long and the coupling still longer in order to afford, besides adequate interthreading between the coupling and secondary rod section for a firm lock of the latter to the associated end piece, a relatively long range within which the main rod section and coupling may securely be interthreaded.

It is another object of the present invention to provide an ignition electrode unit of this type of which the end pieces on the spacer sleeve are advantageously identical and preferably of no more than usual length at which the long coupling of the aforementioned variable-length conductor assembly projects into the spacer sleeve beyond the electrically shielding recess in the associated end piece for a considerable distance over which the coupling is nevertheless electrically shielded from the spacer sleeve in exceedingly simple manner by a bushing of insulating, preferably ceramic, material which is tightly received with one end in the recess of the associated end piece and surrounds the coupling at least over the extent of its projecttion into the spacer sleeve.

It is a further object of the present invention to provide an ignition electrode unit of this type of which the long coupling of the variable-length conductor assembly is within the axial confines of its receiving recess in the associated end piece enlarged into a polygonal, and preferably hexagonal, head over which to apply a socket wrenchthrough the recess for tightening the coupling into firmclamping engagement with the end piece, while the aforementioned electrically-shielding bushing is tightly received in this same recess beyond the enlarged coupling head therein. With this arrangement, the rod sections and coupling are readily assembled not only into the conductor but also simultaneously with the rest of the unit, by inserting the secondary rod section into the associated end piece and clamping it thereto with the coupling, then applying the bushing over the coupling and to the end piece thereat, and finally inserting the main rod section through the other end piece and threatening it into the coupling,

Another object of the present invention is to provide an ignition electrode assembly of this type in which the aforementioned bushing is for its secure mount in the recess in the associated end piece received therein with a loose fit within relatively wide tolerances for its effortless insertion thereinto with some applied cement, however, which on hardening will securely lock the bushing to the endpiece against separation therefrom under any conditions. With this preferred cement lock of the bushing t the associated end piece, a pitted electrode is best replaced by disconnecting the main rod section from the coupling, and removing the secondary rod section and associated end piece, coupling and bushing as a unit from the spacer sleeve and replacing it with a new unit of the same parts.

Further objects and advantages will appear to those skilled in the art from the following, considered in conjunction with the accompanying drawings.

In the accompanyingdrawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

FIG. 1 is a perspective view of an installed ignition electrode unit embodying the present invention;

FIG. 2 is an enlarged section through the installed unit taken substantially on the line 22 of FIG. 1;

. FIG. 3 is a section through the unit taken on the line 3-3 of FIG. 2; and

FIG. 4 is a section through a modified ignition electrode unit. 7

Referring to the drawings, and more particularly to FIG. 1 thereof, the reference numeral 10 designates an ignition electrode unit which is shown installed in the present instance, in the front wall of a bakery oven or the like. The front wallof the oven comprises outer and inner walls 12 and 14, respectively, and the space therebetween is new ally filled with suitable heat-insulating material (not shown). Interposed between the outer and inner oven walls 12 and 14 is a sleeve 16 through which to introduce into the interior of the oven the instant electrode unit 10 as well as a gas supply pipe 18 for a gas burner unit 20 having the flame side 22. The outer ends of the gas supply pipe 18 and electrode unit 10 are suitably mounted in a cover plate 24 on the outer oven wall 12.

Thus, the outer end of the electrode unit 10 may removably be mounted in the cover plate 24 by means of a set screw 26 (see also FIG. 2). The inner end of the electrode unit 10 may conveniently be secured to the burner unit 20 by means of a strap 28. The cover plate 24 is preferably also provided with a peephole which is normally closed by a pivoted cover 30. The cover 30 may be turned into open position to observe through the peephole the ignition of the burner unit 20 at the flame side 22 thereof, as well as the flames themselves for their possible regulation if necessary. The tip 32 of the sparking electrode 34 of the ignition unit 10 is in this instance shown somewhat bent into proximity to the flame side 22 of the burner unit 20, and the strap 28 may conveniently be interrupted at 36 so that the sparking action of the electrode tip 32 may be observed through the peephole in the cover plate 24.

As shown in FIG. 2, the ignition electrode unit 10, hereinafter sometimes referred to as unit comprises two preferably cylindrical end pieces 38 and 40 of heatresistant and electrically non-conductive ceramic material, an electrical conductor 42 in the form of a conductor rod, and an outer spacer sleeve 44 of steel or any other suitable heat-resistant material between the ceramic end pieces 38 and 40. The end pieces 38 and 40 have diametrically reduced portions 46 and 48, respectively, which are received with a sliding fit in the spacer sleeve 44, and the opposite ends of the latter bear against annular shoulders 50 and 52 on the end pieces 38 and 40, respectively. Extending with a sliding fit through apertures 54 and 56 in the end pieces 38 and 40, respectively, is the conductor 42. The conductor 42 may in its inner end press-fittedly or otherwise securely receive the sparking electrode 34 which may be an electrical conductor of any suitable, especially heat-resistant metal, such as commercially known Nichrome, for instance.

The conductor 42 is near its inner end provided with preferably diametrically opposite cars 68 which are conveniently swaged from thesolid rod stock of the conductor and serve as shoulders to bear against a washer 70 on the adjacent end of the ceramic end piece 40. Surrounding the outer end of the conductor 42 is a preloaded compression spring 72 which is interposed between washers 74 and 76, of which the washer 74 rests against the adjacent end of the ceramic end piece 38 (FIG. 2). Re ceived on the threaded outer end of the conductor 42 is a suitable terminal 78 for wiring w (FIG. 1). The terminal 78 serves also to hold the other washer 76 in place. The spring 72 thus serves yieldingly to hold the spacer sleeve 44 and end pieces 38 and 40 in their end-to-end assembled relation.

In use of the unit 10, the same is subjected to the very considerable internal oven heat, with the result that there occurs different thermal expansion of the conductor 42 and spacer sleeve 44 which are, for example, of copper and steel, respectively, and hence have diiferent coefiicients of expansion. With the instant construction of the unit 10, differential expansion of the conductor 42 and spacer sleeve 44 fails to set up any harmful stresses in the unit, and especially in the readilybreakable ceramic end pieces 38 and 40, with the spring 72 acting to take up any differential expansion of the conductor and sleeve parts 42 and 44, as will be readily understood.

In order to hold the tip 32 of the sparking electrode 34 in correct igniting relation with the flame side 22 of the burner unit 20, the conductor 42 is locked, in a man ner to-be-described, at least to the end piece 40 against rotation relative thereto, and preferably both end pieces 38 and 40 are locked to the spacer sleeve 44 against rotation relative thereto. To the end of thus locking the end pieces to the spacer sleeve, the respective diametrically reduced portions 46 and 48 of these end pieces are provided with flats 80 and 82, and the adjacent ends of the spacer sleeve 44 are conveniently deformed, preferably in the manner indicated at 84 in FIGS. 2 and 3, so as there to be in interlock with these flats 80- and 82. Of course, the ends of the spacer sleeve 44 are thus deformed prior to the insertion of the end pieces 38 and 40 therein, and preferably over a steel arbor conforming in cross-sectional shape and dimensions to either reduced portion 46 or 58 of an actual ceramic end piece 38 or 40, so that on subsequent insertion of the actual end pieces 38 and 40 their reduced portions 46 and 48 are in fairly close form-fit with the respective deformable ends of the spacer sleeve 44.

For locking the conductor 42 to the end piece 40 against rotation relative thereto recourse may be had, and in this instance is bad, to a spline connection 90 between them which comprises preferably two opposite grooves 92 in the wall of the aperture 56 in the ceramic end piece 40 (see also FIG. 3), and a like number of key formations 94 on the conductor 42 which are slidably received in the grooves 92, with these key formations 94 being conveniently swaged from the solid rod stock of the conductor 42. However, it is this spline connection which is also used in my aforementioned prior ignition electrode unit and which affords some slight, but nevertheless objectionable, rotary play of the sparking electrode in the mounted unit, in that it makes it impossible to lock the electrode in optimum ignition relation with the flame side of the associated burner. This is due to unavoidable wide tolerances in such a spline connection, considering the relatively wide dimensional variations occurring in finish-forming the grooves in the process of making the ceramic end pieces, and even wider variations in the dimensions of the key formations on the conductor by virtue of their simple swaging from the solid rod stock and enusing inherent poor sizing.

In accordance with an important aspect of the present invention, the objectionable rotary play of the sparking electrode in the mounted unit is overcome by firmly locking it in the unit against such play without, however, interfering in the slightest with the described harmless differential expansion of the conductor 42 and spacer sleeve 44 under heat. To this end, and as shown in FIG. 2, the conductor 42 has a threaded length 96 which on the inside of the end piece 40 receives a nut 98 which on being tightened against the latter firmly clamps the conductor to this end piece between the washer 70 and this nut 98. The ignition electrode unit in FIG. 2 embodies another important feature of the present invention, in that the conductor 42 is formed in two separate rod sections 100 and 102, of which section 100 is relatively short and received in the end piece 40, while section 102 is much longer and received in the other end piece 38, and the nut 98 is in the form of a coupling which, in addition to clamping rod section 100 to the end piece 40, also connects both rod sections 100 and 102 and is for that reason of electrically conductive material. For connection of the rod sections 100 and 102, adjacent end lengths 104 and 106 thereof are threaded, and the coupling 98 is in the form of an internally threaded sleeve receiving the threaded end lengths 104 and 106 of the rod sections 100 and 102. In order to apply the coupling 98 to the rod section 100 and tighten the same against the end piece 40 for firmly clamping this rod section to the latter, the other rod section 102 and its end piece 38, or preferably the rod section 100 with its end piece 40, are disassembled from the rest of the unit for access with the coupling 98 to the rod section 100. Further, for quick application of the coupling 98 to the rod section 100 and equally quick and effortless tightening of the coupling against the end piece 40, the sleeve coupling 98 has an end formation, in this instance an enlarge polygonal, preferably hexagonal, head 108 for application thereto of a suitable tool, in this case a socket wrench (not shown). With the coupling 98 thus tightened and the rod section 100 thereby firmly clamped to the end piece 40, the unit is assembled, including driv- 6 ing the threaded end 104 of the rod section 102 into the coupling 98, as will be readily understood.

In accordance with another aspect of the present invention, the rod sections 100, 102 and their connecting coupling 98 are arranged for assembly into a conductor 42 of reltaively widely variable length to accommodate ignition electrode units of equally widely different lengths. To this end, the threaded end length 104 of the rod section 102 is far longer than would be required for its mere secure connection with the coupling 98, and the latter is even much longer not only to provide a fairly long range within which the rod end 104 may be securely interthreaded with the coupling for different lengths of the assembled conductor 42, but also to provide at any interthread of this rod end with the coupling anywhere within this range a gap g between the adjacent ends of the rod sections and 102 which is sufliciently long to avoid possible spark jumping thereacross and thus compel the heavy operating current to pass through the conductive coupling and bypass this gap.

With the cross-sectional dimensions of the spacer sleeve 44 being for practical reasons preferably kept at a minimum at which the exposed conductor rod section 102 therein has adequate clearance from the surrounding spacer sleeve safely to avoid spark jumping from the former to the latter, provisions are made to avoid under any circumstances likely spark jumping from the conductive coupling to the surrounding spacer sleeve owing to the smaller clearance of the former from the latter. To this end, the end piece 40 is in its inner face provided with a recess 112 for the reception of the head 108 of the sleeve coupling 98, with this recess 112 being of sufliciently large cross-sectional dimension, i.e., diameter, to leave between the same and the coupling head 108 clearance c for the reception of a beforementioned socket wrench with freedom to turn it for driving the coupling 98 onto the rod section 100 and tightening it against the end piece 40. However, while the head 108 of the coupling 98 is thus electrically shielded from the surrounding spacer sleeve 44, a considerable remaining length of the conductive coupling 98 also requires such shielding from the surrounding spacer sleeve. While this could be achieved by simply making the end piece 40 considerably longer and the recess 112 therein of sufiicient depth to receive the entire coupling 98, such is not desirable and is even impractical. Thus, the end piece 44 is, despite its relatively small cross-sectional dimensions in conformity with those of the spacer sleeve 44, nevertheless a formidable mass of ceramic material which absorb considerable heat that has to dissipate through the unit, wherefore adding to this ceramic mass by making the end piece considerably longer would all too readily lead to overheating, and ensuing early deterioration, of the unit, include its electrode 34. Overheating of the unit would be particularly severe at the increased length of the end piece 40 required electrically to shield from the spacer sleeve 44 the entire coupling 98 of the described exceptional length. Also, since for the sake of economy in producing the end pieces and assembling them with the rest of the unit, both end pieces 38 and 40 are preferably identical, this is all the more reason for keeping these end pieces at the smallest possible dimensions, including length. It is for these reasons far preferable to keep the identical end pieces 38 and 40 at reasonable length at which only part of the length of the coupling 98 is shielded from the spacer sleeve 44 by the end piece 40, and to resort to an auxiliary shield for the remaining length of the coupling 98. This auxiliary shield is an electrically insulating bushing 114, preferably of ceramic, which with one end is tightly mounted in the open end of the recess 112 in the end piece 40 beyond the coupling head 108 therein, and surrounds the remainder of the coupling to shield the same from the spacer sleeve 44. The ceramic bushing 114 is preferably kept at outside and inside diameters for its relatively loose fit in the open end of 7 the recess 112 and easy slippage of, the same over the sleeve coupling 98. To avoid separation of the ceramic bushing 114 from the ceramic end piece 40 under these circumstances, the bushing 114 is preferably cemented in therecess 112.

In the event that the sparking electrode 34 becomes pitted and requires replacement, such replacement is readily achieved by disconnecting the conductor rod sec tion 102 from the coupling 98 and retracting from the unit the end piece 40 with the therewith assembled rod section 100 and bushing 114, then inserting into the unit a new assembly of the same parts and connecting theold rod section 102 with the new coupling 98. v

In the described ignition electrode unit of FIG. 2, the loose spline connection 90 between the end piece 40 and conductor rod section 100 is used because it affords in the assembly of the unit quick, though somewhat loose, orientation of the sparking electrode 34 in the unit for its subsequent approximate alignment with the flame side of an associated burner on mounting the unit according to an established pattern in the cover plate 24 of an oven installation (FIGS. 1 and 2), such as, for example, with the deformed front end 84 of the spacer sleeve 44 being turned to face upward (FIG. 2). However, even though this loose spline connection is desirable for this reason, it in nowise detracts from the important advantagesof the coupling 98 to lock the electrode 42 firmly in the unit against any, and even the slightest, rotational play, and further to aflord adjustment of the electrode of. the mounted unit in optimum ignition relation with an associ ated burner and then lock it in such optimum .relation. Of course, it is entirely feasible and fully wtihin the ambit of the present invention, to dispense with the loose spline connection 90 between the end piece 40 and rod section 100, and to rely solely on the lock of the conductor to the end piece 40 by the coupling 98 in holding the electrode in optimum igniting relation with an associated burner. Also, while in the described ignition electrode unit 10 the enlargedhead 108 of the coupling '98 isof preferred hexagonal shape for the application of a socket wrench thereto, it is also within the purview of the invention to provide this coupling head 108 with a cylindrical periphery and provide the coupling with another formation for reception of a driving tool, such as having in the opposite end of the sleeve coupling a diametrical groove for-application of a screwdriver, for example. 7 I

While the described ignition electrode unit 10 of FIG. 2 has both features of locking the electrode in the unit against any rotational play and also forming the conductor in sections for their assembly into a conductor of different lengths, FIG. 4 shows a modified ignition elec-, trode unit 10a in which the conductor 42a is not formed in separate sections but is a single rod, but this conductor rod is locked in the unit against rotational play by a nut 98a which in electrically shielded fashion is received in a recess 112a in the ceramic and piece 40a, with the nut98a being received by a threaded intermediate length 120' of the conductor rod 42a.

What is claimed is: Y 1. An ignition electrode unit, comprising two apertured ceramic end pieces; a spacer sleeve interposed between and abutting said end pieces, with at least one of said end pieces being locked to said sleeve against rotation relative thereto; a conductor rod extending through said sleeve with clearance therefrom and slidably received intermediate its ends in said apertures in said'end pieces, with said rod having a threaded length in said sleeve, and one end of said rod. next to said one end piece having a shoulder abutting the latter, and a projecting electrode; a part removably carried by the other end of said rod; a loaded spring interposed between said part and the other end piece yieldingly holding said end pieces and sleeve in said 8 abutting relation and taking up differential expansion of said rod and sleeve on subjection of the unit to heat; and a nut received on said threaded rod length and tightened against said one end piece to clamp said rod to the latter.

2. An ignition electrode unit as in claim 1, in which said one end piece has an inner face in said sleeve and a recess in said inner face centered on, and of largecrosssectional dimension than, said aperture therein, and said nut is received in said recess so asv to be electrically shielded from the surrounding sleeve.

3. An ignition electrode unit as in claim 2, in which said nut has an outer polygonal periphery, and the crossectional dimension of said recess is sufficiently large to receive a socket wrench over said polygonal nut periphery.

4. An ignition electrode unit as in claim 1, in which said rod is formed in separate aligned short and long sections received in said one and other end pieces, respectively, with said short and long rod sections having adjacent threaded end lengths and providing said shoulder and carrying said part, respectively, and said nut is an electrically conductive coupling threadedly received by said end lengths of said rod sections to connect the latter, and also tightened against said one end piece to clamp said short rod section to the latter.

5. An ignition electrode unit asvin claim 4, in which said coupling has a formation operatively engageable with a tool for turning said coupling."

' 6. An ignition electrode unit as in claim 4, in which said one end piece has an inner face in said sleeve and a recess in said face centered on, and of larger cross-sectiona1 dimension than, said aperture therein, said coupling is aninternally threaded sleeve with an enlarged polygonal I head at one end, of which said head, is received in said recess with sutficient'clearance therefrom to apply a socket wrench thereto with freedom to turn in said recess, thereby electrically shielding said sleeve head from the surrounding spacer, sleeve.

7. An ignition electrode unit as in claim 6, in which said threaded sleeve is longer, and said head thereof is shorter, than the depth of said recess, and there is further provided a bushing of electrical insulation material mounted with one end insaid recess next tosaid sleeve head therein and surrounding said threaded sleeveat least to its other end, whereby said entire threaded sleeve is electrically shielded from the spacer sleeve.

8. An ignition electrode unit 'as in claim 7, in which said bushing is of ceramic material.

9. An ignition electrode unit as in claim 8, in which said one end of said ceramic bushing is cemented in said recess.

10. An ignition electrode unit as in claim 1, in which said rod is formed in separate aligned first and second sections received in'said one and other end pieces, respectively, with said first and second rod sections having adjacent threaded end lengths and providing said shoulder and carrying said part, respectively, and said nut is an electrically conductive coupling threadedly received by said end lengths of said rod sections to connect the latter, and also tightened against said one end piece to clamp said first rod section to the latter.

References Cited UNITED STATES PATENTS VOLODYMYR Y. MAYEWSKY, Primary Examiner US. Cl. X.R. 313-238, 255 

